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Some Important Compounds of Transition Elements

  • Last Updated : 19 Jan, 2022

Transition metals are typically characterized as elements with or capable of forming partially filled ‘d’ orbitals. Transition elements are d-block elements in groupings of three to eleven. Inner transition metals, which include the lanthanides and actinides, are another name for the f block elements. This requirement is also met because the d orbital is only partially occupied before the f orbitals.

The d orbitals are typically filled with the copper family, which is group 11, and as a result, the next in the family, group 12, is technically not defined as transition element compounds. However, the group 12 elements share some of the same chemical properties and are frequently included in discussions about transition metals. Some scientists, however, classify the elements of Group 12 as transition metals.

The elements of the d-block are separated into three transition series: Sc through Cu, Y through Ag, and Hf through Au. Ac is the initial element in the fourth transition series, which also includes Rf and Rg. The f-block elements are the elements Ce through Lu, which form the lanthanide series, and Th through Lr, which form the actinide series.

Lanthanum behaves extremely similar to the lanthanide elements, which is why it is classified as a lanthanide element, despite the fact that its electron configuration places it at the beginning of the third transition series. Similarly, actinium’s behavior indicates that it belongs to the actinide series, despite the fact that its electron configuration places it as the initial member of the fourth transition series.

Compounds of Transition Elements

  • Ferrous Sulphate (Green Vitriol), FeSO4.7H­2O

Anhydrous and hydrated FeSO4 is both green and white in color. It has the same isomorphism as Epsom salt, MgSO4.7H2O, and ZnSO4.7H2O. When exposed to air, it effervesces. It absorbs HNO3 like other ferrous salts, generating the brown-colored double complex Fe(NO)SO4, nitroso ferrous sulfate. It forms double salts with alkali metal sulfates. It reacts with ammonium sulfate to generate ferrous ammonium sulfate, often known as Mohr’s salt, FeSO4.(NH4)2SO4.6H2O. It has no effervescence. In solution, it ionizes to form Fe2+, NH4+, and SO42– ions.

  • Ferric Oxide, Fe2O3

The anhydrous salt is a yellow, deliquescent substance that is very soluble in water. When heated, it produces FeCl2 and Cl2. Because of hydrolysis, its aqueous solution is acidic.

  • Silver Nitrate, AgNO3

With various salt solutions, silver nitrate precipitates, which aids in the detection of acid radicals. It decomposes when heated.

  • Mercury (I) Chloride (Hg2Cl2)

It is a white powder that is soluble in chlorine water but not in water. It turns black when treated with ammonia due to the creation of finely split mercury.

  • Mercury (II) Chloride (HgCl2)

It is a white crystalline substance that is only sparingly soluble in cold water but completely soluble in hot water. By adding Cl, its solubility can be increased. It is converted to mercury when handled with SnCl2.

  • Mercury-II Iodide

Mercuric iodide comes in two colors: red and yellow. Above 400 K, the yellow form is stable, while the red form is stable below this temperature. Nessler’s reagent is an alkaline solution of K2HgI4 that is used to detect the presence of NH4+ by producing a brown precipitate due to the creation of iodide of Million’s base.

  • Copper(II) Sulphate Pentahydrate or Blue Vitriol (CuSO4.5H2O)

It has 5 water molecules of crystallization, all of which can be eliminated by heating to yield colorless CuSO4. When heated at a high temperature, it produces cupric oxide. Iodine is liberated from soluble iodides. It is used as an electrolyte in copper electroplating, electrotyping, and refining. It is used to keep weeds at bay in reservoirs and swimming pools.

  • Potassium Dichromate (K2Cr2O7

Because sodium and potassium dichromates are strong oxidizers, acidified K2Cr2O7 will oxidize iodides to iodine, sulfides to sulfur, tin (II) salts to tin (IV), and iron (II) salts to iron (III). In volumetric analysis, it is employed as an oxidizing agent. It is also used in mordant dyes, the leather industry, photography (for film hardening), and chromyl chloride tests. It’s used to clean glassware.

Conceptual questions

Question 1: What are the metallic qualities of the transition metals?


Transition metals have typical metallic qualities such malleability, ductility, high tensile strength, and metallic lustre. They are often good heat and electrical conductors and crystallise in BCC, CCP, or HCP structures. Trends in the metallic characteristics of the transition elements, on the other hand, can be seen. Because they contain a large number of unpaired electrons, elements such as chromium and molybdenum are among the hardest transition metals.

Question 2: Why are some transition metals referred to as Noble Metals?


Noble metals are elements in the lower right corner of the contemporary periodic table’s d-block (such as gold, silver, and platinum). Because of their low hydration enthalpies and high ionisation enthalpies, these metals are very unreactive. These metals are extremely resistant to acids. Metals such as platinum, mercury, and gold, on the other hand, can be dissolved in various acid mixes such as aqua regia (a mixture of hydrochloric acid and nitric acid). Silver, it should be noted, does not dissolve in aqua regia.

Question 3: Why Is It called transition metals?


Transition metals are found in the periodic table between the s-block and p-block elements. They’re known as d-block elements. Because these metals are unstable and display transitional behaviour between s and p block elements, they are referred to as transition metals.

Question 4: Why do we see different colors among transition elements?


When they start bonding with other ligands, the d orbitals split apart and become non-degenerate due to differing symmetries of the d orbitals and the inductive effects of the ligands on the electrons. The energy of excitation relates to the frequency of light absorbed when an electron jumps from a lower energy d orbital to a higher energy d orbital, which is referred to as a d-d transition. As a result, light waves give the energy required by electrons to shift. The frequency of a light wave is found to be in the invisible range. The type of the ligands influences the frequency of light absorbed.

Question 5: Are inner transition metals reactive?


The inner transition metals, which are normally found at the bottom of the Periodic Table, are found in the f-block. They are nearly as reactive as alkali metals, and all actinides are poisonous and have no commercial utility. Nonetheless, radioactive elements have the potential to be utilised as weapons or in nuclear power plants.

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